1. Field of the Invention
The present invention relates to a safety device for an automotive air conditioning system using engine cooling water as heat source for air conditioning the passengers' compartment of an automobile, capable of discharging the engine cooling water when the temperature of the engine cooling water exceeds a predetermined temperature level or when the pressure of the engine cooling water exceeds a predetermined pressure level.
2. Description of the Prior Art
Generally, an automotive air conditioning system uses engine cooling water as heat source for air conditioning the passengers' compartment of an automobile. As shown in FIG. 14, the water cooling system for cooling the engine is a closed circuit formed by interconnecting the water jacket of an engine 1, a radiator 2 and a heater core 3 by pipes P.sub.1 and P.sub.2. The engine cooling water in the pipes P.sub.1 and P.sub.2 is urged by a water pump 4 which is driven by the engine 1 so as to flow through the radiator 2 and the heater core 3 in order to cool the engine 1 and to air-condition the passengers' compartment. (Refer to Japanese Utility Model Laid-Open No. 60-122,208).
Accordingly, the engine cooling water circulates through a radiator circuit R formed by interconnecting the radiator 2 and the engine 1 by the pipe P.sub.1 and through a heater core circuit H formed by interconnecting the heater core 3 serving as a heat source of the automotive air conditioning system and the engine 1 by the pipe P.sub.2.
The flow rate of the engine cooling water circulating through the radiator circuit R is regulated by a thermostat 5 which regulates the cross-sectional area of the flow passage of the radiator circuit R. The flow rate of the engine cooling water circulating through the heater core circuit H is regulated by means of a water cock 6 provided near the heater core 3 in the heater core circuit H. When the temperature of the engine cooling water circulating through the radiator circuit R exceeds a predetermined temperature level or when the pressure of the same exceeds a predetermined pressure level due to some cause, a safety valve (not shown) incorporated into the radiator cap 7 opens to discharge the engine cooling water from the radiator 2 so that the radiator circuit R is relieved of the high-temperature or high-pressure engine cooling water.
That is, although the water cooling system comprises the radiator circuit R and the heater core circuit H, the water cooling system is a single closed circuit as a whole, and hence the safety of the heater core circuit H can naturally be secured by relieving the radiator circuit R of the high-temperature or high-pressure engine cooling water by the safety valve provided in the radiator circuit R.
The safety valve incorporated into the radiator cap 7 functions according to the pressure of the engine cooling water.
In the winter season, it is possible that the radiator circuit R is clogged in the vicinity of the safety valve where the flow passage becomes narrow by the frozen engine cooling water or changing into the sherbet state. In such a clogged state, the safety valve is unable to function normally and the engine cooling water flows excessively through the heater core circuit H having a comparatively small flow capacity, and thereby it is possible that a portion having a low strength of the heater core circuit H is broken due to the flow of the engine cooling water of an abnormally high temperature or an abnormally high pressure through the heater core circuit H.
The breakage of the heater core circuit H causes the engine cooling water containing an antifreeze to leak into the passengers' compartment to soil the floor of the passengers' compartment.
The present invention has been made to eliminate the drawbacks of and to solve the problems of the conventional automotive water cooling system. Accordingly, it is a principal object of the present invention to protect the heater core circuit and the radiator circuit by, discharging the engine cooling water outside the passengers' compartment when the temperature of the engine cooling water flowing in the heater core circuit exceeds a predetermined temperature level or when the pressure of the same exceeds a predetermined pressure level.
It is a second object of the present invention to protect the water cooling system from damage when the safety valve incorporated into the radiator cap becomes inoperative.
It is a third object of the present invention to provide a safety valve capable of readily dealing with the variation of the boiling points and the rising mode of pressure of the engine cooling water containing an antifreeze.